Chip-based fluid channels are used for many different applications. Applications include zone electrophoresis separation of analytes and capillary electrophoresis performed on chip-based substrates. Various spectroscopic detectors are used do detect the analytes. Attempts to couple mass spectrometry with the chip-based fluid channels involve creating an electrospray of analytes, which is directed to an ion sampling orifice of the mass spectrometer.
Several different attempts to deliver analyte from a microchannel in an electrospray include direct spraying from a flat edge of the chip, the use of a pulled glass capillary, a sleeve to support a sprayer capillary on the edge of the chip, and disposable emitters. Still further prior methods include gluing a pulled capillary sprayer on the flat, larger surface of the chip aligned with the channel. An alternative approach employs a microfabricated monolithic nozzle surrounded by an annular cavity on the surface of a silicon substrate. A still further approach involves an integrated miniaturized pneumatic nebulizer is coupled via a sub-atmospheric liquid junction electrospray interface.
Alternatives to spraying from the chip involve the use of miniaturized ion spray devices that are not formed by microfabrication techniques.